Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic.
Department of Forest Botany, Dendrology and Geobiocenology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Brno, Czech Republic.
Physiol Plant. 2021 Aug;172(4):2048-2058. doi: 10.1111/ppl.13435. Epub 2021 May 2.
During soil drought (i.e. limited soil water availability to plants), woody species may adjust the structure of their vessel network to improve their resistance against future soil drought stress. Impacts of soil drought on intervessel lateral contact remain poorly understood despite of its significance to xylem transport efficiency and safety. Here, we analysed drought-induced modifications in xylem structures of temperate angiosperm trees with a focus on intervessel lateral contact. Anatomical analyses were performed both in stems of seedlings cultivated under different substrate water availability and annual rings of mature individuals developed during years of low and high soil drought intensities. In response to limited water availability, a decrease in vessel diameter (up to -20%) and simultaneous increase in vessel density (up to +60%) were observed both in seedlings and mature trees. Conversely, there were only small and inconsistent drought-induced changes in intervessel contact frequency and intervessel contact fraction (typically up to ±15%) observed across species, indicating that intervessel lateral contact is a conservative trait. The small adjustments in intervessel lateral contacts were primarily driven by changes in the contact frequencies between neighbouring vessels (i.e. vessel grouping) rather than by changes in proportions of shared cell walls. Our results demonstrate that angiosperm tree species, despite remarkable adjustments in vessel dimensions and densities upon soil drought, exhibit surprisingly invariant intervessel lateral contact architecture.
在土壤干旱（即植物可利用的土壤水分有限）期间，木本物种可能会调整其导管网络的结构，以提高其对未来土壤干旱胁迫的抵抗力。尽管木质部运输效率和安全性对导管间横向接触有重要影响，但土壤干旱对导管间横向接触的影响仍知之甚少。在这里，我们分析了温带被子植物树木木质部结构在干旱诱导下的变化，重点关注导管间的横向接触。对幼苗在不同基质水分供应下培养的茎和成熟个体在低土壤干旱强度和高土壤干旱强度年份形成的年轮进行了解剖学分析。由于水分有限，幼苗和成熟树木的导管直径（最大减少 20%）和导管密度（最大增加 60%）都有所下降。相反，跨物种观察到的导管间接触频率和导管间接触分数的干旱诱导变化很小且不一致（通常在±15%以内），这表明导管间横向接触是一个保守的特征。导管间横向接触的微小调整主要是由相邻导管之间的接触频率（即导管分组）的变化驱动，而不是由共享细胞壁比例的变化驱动。我们的研究结果表明，尽管被子植物物种在土壤干旱时对导管尺寸和密度进行了显著调整，但它们的导管间横向接触结构却出人意料地保持不变。
